LED display devices have many advantages of pure colors, wide dynamic range, high brightness, high definition, low voltage, low power consumption, long life, impact resistance, wide viewable angle, stability, and reliability. LED display devices have become a new generation of display media and have been used widely.
A display unit of a LED display device includes an LED array and a driving circuit. The main structure of LED is a solid semiconductor chip that may convert electrical energy into visible light. The LED is packaged by a transparent epoxy resin. The LED semiconductor chip includes two parts. One part is a P-type semiconductor dominated by holes inside. The other part is an N-type semiconductor composed mainly of electrons inside. When the P-type semiconductor and the N-type semiconductor are connected, a P-N junction is formed between the P-type semiconductor and the N-type semiconductor. When an electric field is applied between the P-type semiconductor and the N-type semiconductor, electrons in the N-type semiconductor are pushed to the P-type semiconductor, recombined with the holes in the P-type semiconductor, and release energy in the form of photon. This is the light-emitting mechanism of LED. The wavelength of the light emitted from the LED, that is the color of the light, is determined by the material of P-N junction. In Practice, one end of the LED semiconductor chip is attached to a bracket. One end of the LED semiconductor chip is a cathode, and the other end that is connected with a power supply is an anode. Full-color LED display device applies voltages to two ends of the LED semiconductor chip through the driving circuit, controls the on-off state and the brightness of LEDs of multiple colors (generally including red LEDs, green LEDs and blue LEDs), so as to display color pictures.
However, for full-color LED display devices, because the light-emitting units of LEDs of different colors are doped with different composition materials, the process cycle is prolonged, the production costs are raised, and the defect rate of products is increased. In addition, because the drivers and sizes of LEDs of different colors are different, the cell thickness of the LED display panel and the production costs are largely raised. This is on the contrary of the market needs to reduce the thickness and cost of display devices. Thus, the application of LED display device is limited significantly.